1. Field
The present disclosure relates to an electric rotary motor; and, particularly, to a method for binding stator winding coils.
2. Discussion of the Related Technology
In general, a motor necessarily includes a stator having coils wound therein, and the coils are inserted into slots of the stator.
Recently, a demand for miniaturization and high efficiency of a motor has continuously increased.
In order to realize the miniaturization and high efficiency of a motor according to such a demand, the slots of the stator include as many ring-shaped coils inserted therein as possible.
However, because of a dead space formed between a ring-shaped coil and another adjacent ring-shaped coil and another dead space formed between the ring-shaped coil and a stator's teeth, the quantity of the inserted ring-shaped coils is inevitably limited.
Examples of a winding method capable of accomplishing miniaturization and high efficiency of a motor by solving the above-described dead space problem may include a hairpin winding method.
In the hairpin winding method, coils may be wound in slots of a stator without a dead space formed therein. Therefore, the hairpin winding method has an advantage in terms of miniaturization and efficiency.
On the other hand, the hairpin winding method requires high-level manufacturing techniques such as coil forming, coil twisting, and coil welding, and a lot of problems occur during welding.
In particular, when a welding defect occurs while a welding operation is performed or after a welding operation is completed, welded coils are removed, and the stator manufacturing process are performed again. In this case, the damage caused by the welding defect is inevitably high.
Therefore, when the coil forming operation and the coil twisting operation of the hairpin winding method are more simplified, in particular, when the difficulties caused by the welding operation are removed, the advantage of the hairpin winding method in terms of miniaturization and efficiency may be maximized, and the merchantability of motors manufactured by the hairpin winding method may be improved.
In the hairpin winding method, however, a welding operation is performed after the hairpin coils are wound.
Because of the difficulties during the welding operation, coatings of the coils may be burned even though the coils are welded. Furthermore, since four layers are wounded adjacent to each other, coatings of first and second layers may be burned when third and fourth layers are welded, or coatings of the third and fourth layers may be burned when the first and second layers are welded. Furthermore, as primary-side copper loss increases due to an increase of contact resistance during partial welding, the efficiency may decrease at low speed.
The disadvantages of the manufacturing process may include an additional coil process for welding, the use of expensive equipment for correctly performing a welding process and cooling down welding heat, and welding gas which may pollute a work place.
In particular, attention is paid from the start to the end of the welding operation such that a welding defect does not occur. However, as the number of welding operations increases according to the number of stator slots, there is an inevitable limitation.
For example, when the number of stator slots is 72, welding operations are performed 144 times. Therefore, when a welding defect occurs at the 144th welding operation even though the first to 143rd operations are normally performed, all of the welded hairpin coils are removed, and the same process is repeated.
Therefore, the above-described patent document can hardly be free from various problems caused by welding, when manufacturing a motor according to the hairpin winding method which has an advantage in efficiency and output density because of the maximized space factor.